MOSCOW -- Russia may invade southeast Ukraine to protect the local population, President Vladimir Putin said Thursday.

Speaking live at his annual call-in show in a Moscow television studio, Putin implied he reserves the right to move Russian troops into the neighboring country on behalf of pro-Russian residents.

“We know quite well that we must do our best to protect their rights and help them independently decide their fate and we will struggle for that,” Putin said. “I remind you that the Federation Council of Russia [the upper house of Parliament] empowered the president to use the armed forces in Ukraine.”

“Today Putin in fact set up an ultimatum for Kiev to either allow a wide federalization of Ukraine with vast powers for eastern regions allowing Moscow to regain its political and economic control over them without formally annexing them, or to face a full-scale armed invasion resulting from which Moscow will establish its military control over at least the southeast of Ukraine,” Karasyov, director of Kiev-based Institute for Global Strategies, said in a phone interview. “He made his terms quite clear today.”

Putin also reiterated his position that the southeast regions of Ukraine for centuries were Russian territories called Novorossiya or New Russia, and it was the Bolshevik leadership in the early 20th century that handed those regions over to the newly formed Soviet Ukraine.

Putin lashed out at the lack of democracy and attacks on opposition candidates in the course of the current presidential campaign in Ukraine and refused to recognize the legitimacy of the interim government in Kiev.

“We consider the current Ukraine authorities illegitimate as they have no national mandate to run the country,” Putin said.

Putin vehemently denied the alleged involvement of Russian troops and agents in Wednesday's attack on a base in southeastern Ukraine.

“This is all rubbish!” Putin charged emotionally during the TV show. “There are no Russian units, no special services, no instructors. These are all local residents … I told my Western partners: “They have nowhere to go, they will not go away anywhere, they are the masters of their land and they need to be talked to.”

Earlier this week Ukraine's Security Service accused Russia of directing military operations in the Donetsk and Luhansk regions of eastern Ukraine, presenting as proof transcripts and recordings of allegedly intercepted radio and telephone communications between armed terrorists capturing administrative buildings and police stations in the region and their alleged coordinator in Russia.

Putin's TV show was conducted as armed confrontations between separatist forces and Ukraine's regular army, security and police troops were already raging in the region.

Ukraine Acting Interior Minister Arsen Avakov wrote on his Facebook account that Ukraine National Guard troops repelled an attack by armed separatists Wednesday night in the port of Mariupol in southeast Ukraine on the Azov Sea. Three separatists were killed, 13 wounded and 63 taken prisoner, Avakov said.

Earlier Wednesday, armed separatists captured in the town of Kramatorsk in the north of Donetsk region compelled a mechanized detachment of Ukrainian troops deployed in the area to surrender at least six armored personnel vehicles to the insurgents, who raised Russian national flags over them and moved them to the town of Slovyansk under control of separatist forces allegedly led by Russian military intelligence agents.

Putin claimed that pro-Russia residents in the area armed themselves of their own accord and accused Ukraine's interim government of destabilizing the region.

“Instead of realizing that something is going astray in the Ukrainian state and making an attempt to open a dialogue, they began more and more to threaten a use of force and moved tanks and aviation against the civilian population,” Putin said. “It is yet another very serious crime of the current masters of Kiev.”

But Putin for the first time admitted publicly that Russian troops were deployed in Crimea before the referendum to help it be democratically conducted.

Until Thursday, Putin had more than once publicly denied such an involvement, saying the troops in unmarked uniforms who seized administrative buildings, and surrounded and blocked Ukrainian army units in Crimea were local defense forces who could have bought Russian military uniforms in a store somewhere.

“Of course our servicemen stood behind the defense forces of Crimea. They acted with great restraint but … very resolutely and professionally,” Putin said. “Otherwise it was simply impossible to hold the referendum openly, honestly and with dignity and to help the people to express their opinion. You should bear in mind that there were over 20,000 [Ukrainian] well-armed servicemen in Crimea.”

Russia annexed Crimea on March 18 shortly after the referendum, which Ukraine and the United Nations have refused to recognize.

Ukraine's worst unrest since the 1991 collapse of the Soviet Union was sparked by ousted President Viktor Yanukovich's decision to scrap a deal with the European Union in favor of closer ties with Russia.

Russian President Vladimir Putin said Wednesday that he had pulled back troops from the border with Ukraine and called on Kremlin-allied separatists to delay a referendum on whether Ukraine's regions should have a greater degree of autonomy.

At least 14 people were killed and scores were wounded as government forces seeking to win back this eastern Ukrainian city from pro-Russia separatists ran into an ambush Monday set up by the rebel gunmen.

A crowd of more than 2,000 pro-Russia separatists on Sunday night seized one of the last key official sites in the eastern Ukraine city of Donetsk still in the hands of the country’s interim government.

Armed clashes left scores of people dead in Ukraine on Friday, as President Obama and German Chancellor Angela Merkel vowed to impose stiffer economic sanctions on Russia if it disrupts Ukraine's upcoming election.